1. Field
The invention relates to an assembly for controlling fluid delivery via a syringe. In particular, the invention relates to a drive system coupled to the plunger of a syringe which is monitored and contorlled by an optical/electronic feedback system for precisely determining and controlling the position and motion (velocity and acceleration) of the plunger.
2. State of the Art
Present commercial clinical laboratory applications of syringe delivery systems typically include a stepper motor attached to a drive mechanism which is coupled to the plunger of a syringe. A typical example of such systems are digitial pumps such as the Cavro Modular Digital Pump, Model SB, manufactured and sold by Cavro Scientific Instruments, Inc., Sunnyvale California.
In conventional systems, the stepper motor usually has increments of resolution of not less than 1.8.degree. per step (approximately 200 steps per revolution). Furthermore, no positional feedback loop is used to ensure accuracy and detect errors of motion. In practice it is not unusual, for example, that the control to the stepper motor will indicate that a determined number of programmed steps has been taken, but that the stepper motor in fact does not rotate the number of steps programmed. An error in the position of the plunger thus occurs and concomitantly an error in the amount and rate of delivery of fluid from the syringe will occur also. Accordingly, there is a need for an assembly which accurately and precisely controls and monitors the position and motion of the syringe plunger so that accurate amounts of fluid can be delivered. The present invention is considered to provide such assembly.